2002 Honda CRV check engine light

Those refer to the heaters in the oxygen sensors. The codes are specific to Honda. Here's what I found:

"When is the code detected?
If the element is not activated or the Engine Control Module (ECM) terminal voltage is a set value or less for at least a set time period when the power is drawn to the A/F sensor (sensor 1) heater, a malfunction is detected and the code is stored.

P1166, 67 Honda Description

The Air/Fuel Ratio (A/F) sensor 1 is installed in the exhaust system and detects oxygen content in the exhaust gas. The A/F sensor transmits output voltage to the Engine Control Module (ECM). A heater for the sensor element is embedded in the A/F sensor (sensor 1). It is activated and heats the sensor to stabilize and speed the detection of oxygen content by controlling current flowing through the heater. An increase in the current levels off as the applied voltage to the element electrode reaches a certain range because the amount of oxygen which is led through the diffusion layer is limited. The current amperage is proportional to oxygen content in the exhaust gas, so the air/fuel ratio is detected by the measurement of the current amperage. The ECM compares a set target air/fuel ratio with the detected air/fuel ratio and controls the fuel injection timing.

If the A/F sensor (sensor 1) voltage is low, the air/fuel ratio is lean, and the ECM uses A/F feedback control to issue a Rich command. If the A/F sensor (sensor 1) voltage is high, the air/fuel ratio is rich, and the ECM uses A/F feedback control to issue a Lean command.

Possible causes
- Faulty Air/Fuel Ratio Sensor 1
- Air/Fuel Ratio Sensor 1 harness is open or shorted
- Air/Fuel Ratio Sensor 1 circuit poor electrical connection

We normally call that the oxygen sensor since that's all they detect. You want the one in front of the catalytic converter. The Engine Computer constantly adjusts the fuel metering calculations based on its readings. When warmed up and working properly, this sensor's readings will switch between "rich" and " lean" about two times per second.

There is also a rear, or "downstream" oxygen sensor. It is only used to monitor what comes out of the catalytic converter to be sure the exhaust was cleaned up. That one might switch between rich and lean perhaps as little as once every minute or two.